1. Field of the Art
This invention relates to an ultrasound endoscope having an electronic scan type ultrasound transducer incorporated into a rigid tip end section at the distal end of an elongated insert section along with an optical observation means.
2. Prior Art
Ultrasound endoscopes have both an optical observation means and an ultrasound examination means on a rigid tip end section of an elongated flexible insert section to be inserted into a body cavity. The optical observation means is composed of illumination components and an optical image pickup system for observation of intracavitary sites of interest. Normally, picture images of an intracavitary site are captured by a solid-state image sensor. On the other hand, the ultrasound examination means is constituted by an ultrasound transducer which is categorized either as a mechanical scan type or as an electronic scan type depending upon the operating mode of the ultrasound transducer. An electronic scan type ultrasound transducer is provided with a plural number of transducer elements which are arrayed in a predetermined direction and are sequentially activated to make an ultrasound scan over a predetermined range.
As described in Japanese Laid-Open Patent Application H10-118072, for example, in the case of an ultrasound endoscope with an electronic scan type ultrasound transducer, an ultrasound transducer is mounted on a rigid tip end section at the distal end of an endoscopic insert section, and illumination or lighting components and an image pickup system of the optical observation means are mounted behind the ultrasound transducer. In that prior art ultrasound endoscope, a large number of ultrasound transducer elements are arrayed in a convexly arcuate shape in the axial direction of the rigid tip end section. The casing of the rigid tip end section is sloped upward behind the ultrasound transducer to provide a inclined casing wall section for fitting the illumination components and image pickup system of the optical observation means which has a view field in an obliquely upward direction, providing a slant view endoscope.
Tomographic information of body tissues can be obtained by activating the ultrasound transducer for an ultrasound scan. In case a disorder is found in body tissues, a treatment or sampling of body tissues can be made by the use of a puncture instrument. For this purpose, a biopsy channel is provided through the insert section of the endoscope for insertion of a biopsy or surgical or other medical instrument. The biopsy channel is constituted by a flexible tube up to a point immediately on the proximal side of the rigid tip end section of the insert section, namely, as far as a fore end of a bending section which is provided on the proximal side of the rigid tip end section to turn the latter into a desired direction. By the use of a connecting pipe, the flexible tube of the biopsy channel is connected to a tunnel-like terminal passage which is provided internally of the casing of the rigid tip end section. A fore end portion of the connecting pipe is inserted into the tunnel-like terminal passage while its rear end portion is projected into the bending section by a predetermined length, and fore end the flexible tube is joined with the rear end of the connecting pipe in the bending section by fitting engagement with the latter. Accordingly, the biopsy channel is constituted by a straight passage which is extended in the axial direction of the insert section as far as the angle section on the proximal side of the rigid tip end section. Past the bending section, the biopsy channel is constituted by a terminal passage which is turned upward or radially outward in the forward direction. An opening at the fore end of the tunnel-like passage forms an instrument outlet in the afore-mentioned inclined wall section of the casing of the rigid tip end section, in which illumination components and image pickup system of the optical observation means are fitted. Thus, a biopsy or surgical instrument which is projected out of the biopsy channel can be captured in the view field of the endoscopic observation means.
In case a diseased portion or a site of particular interest is spotted in body tissues under an ultrasound examination, for example, tissue cells are sampled for the purpose of close examination. A puncture instrument to be stabbed into an intracavitary wall for this purpose is normally provided with a sharp-pointed metal pipe needle of a predetermined length at one end of a flexible tube.
In order to control movement of the sharp-pointed puncture instrument in a safe and secure manner, it is monitored by the optical observation means until it comes into contact with an intracavitary wall. After penetration into an intracavitary wall, the puncture needle is monitored by the ultrasound examination means. The monitoring by the optical observation means is started as soon as the puncture instrument is led out of the instrument outlet opening of the biopsy channel. Once the puncture instrument is projected out of the instrument outlet, the inserted medical instrument should be monitored by the optical observation means every moment without a blind period in which the inserted medical instrument gets out of a view field of the monitoring optical observation means during a movement over a certain distance. Such a blind distance, if any, should be limited to a minimum. Further, the view field of the optical observation means can be limited depending upon the position of the instrument outlet which is opened in a casing wall of the rigid tip end section. Heretofore, from the standpoint of securing a suitable optical observation view field, the instrument outlet opening is opened in a inclined casing wall section in which the optical observation means is accommodated. That is to say, it has been the conventional practice to provide the instrument outlet of the biopsy channel in the proximity of the optical observation means.
Further, a terminal passage which leads to the instrument outlet plays an important role in stabilizing an inserted medical instrument and aiming same at a target point. For these functions, it is desirable for the terminal passage to have a sufficient length. If an inserted medical instrument gets out of the view field of the optical observation means over a certain distance after extrusion from the instrument outlet in the casing of the rigid tip end section, the unguided blind distance might give rise to not only safety problems but also problems in stabilizing and controlling movements of the inserted medical instrument at instant of protrusion through the instrument outlet of the biopsy channel.
As explained hereinbefore, normally an ultrasound transducer is mounted on a rigid tip end section of an ultrasound endoscope, on the front side of an optical observation means which is fitted in a inclined casing wall section and arranged to have a view field in an obliquely upward direction. However, in the case of an electronic scan type ultrasound transducer, a large number of ultrasound transducer elements are arrayed in a convexly arcuate shape in the axial direction of the rigid tip end section, so that the view field of the optical observation means is necessarily limited by the ultrasound transducer to a certain degree. In this regard, even if a casing wall with the instrument outlet opening is located within a view field of an optical observation means, it gives no affects in particular on the endoscopic observation by the optical observation means as long as it is in a range where the view field of the endoscopic observation means is limited by the ultrasound transducer.